1. Field of the Invention
The present invention is related to specific types of pigment compositions which are especially suited to both oil-based and water-based systems, as well as processes for flexographic printing using these pigment compositions. More particularly, the pigment composition of the present invention comprises an alkali blue pigment. The pigment composition of the present invention exhibits a high strength and soft texture in comparison with prior art pigment compositions made from similar ingredients.
2. The Related Art
The closest related art of which applicants are aware includes the following U.S. Pat. Nos.: 4,456,485; 4,383,865; 4,032,357.
U.S. Pat. No. 4,383,865, to Iyengar, discloses a process for preparing a soft textured, high strength Alkali Blue pigment composition which comprises insolubilized amines. This composition is made by mixing a solution of alkali blue crude first with an alkaline solution of an alkyl aryl sulfonic acid, then with an acidic solution having from 3 to 36 carbon atoms, following which the pigment composition is recovered. In the '865 patent the preferred group of alkyl aryl sulfonic acids has from 1 to 14 carbon atoms. The most preferred alkyl aryl sulfonic acid appears to be dodecylbenzene sulfonic acid.
U.S. Pat. No. 4,456,485, also to Iyengar, discloses a process for preparing easily dispersible high color strength powdered alkali blue pigments by precipitating the pigment in the presence of various acids and/or amines, and/or esters, and/or alcohols, etc., as well as the product of these processes.
U.S. Pat. No. 4,032,357, assigned to Sherwin-Williams Company, discloses a substantially anhydrous, free-flowing alkali blue pigment composition having an organic anionic dispersant coprecipitated therewith. Furthermore, the pigment and dispersant are admixed with an oil phase in order to reduce the hydrophilic aggregation of the coprecipitated pigment and dispersant. The specific organic dispersants used in the '357 patent are Gafac.RTM. RS-710 and Gafac.RTM. RS-610.
As can be seen in the appended claims, the scope of the present invention is limited to pigment compositions comprising alkali blue pigment in combination with:
(1) di- and tri- decyl phosphate esters of free acids; and PA0 (2) dehydroabietyl amine. PA0 (a) between 60 percent, by weight, and 98 percent, by weight, alkali blue pigment particles; PA0 (b) between 1 percent by weight and 20 percent by weight of a surfactant selected from the group consisting of di- and tri- decyl phosphate esters of free acids; PA0 (c) between 1 percent by weight and 20 percent, by weight, of dehydroabietyl amine, said weights based on the total composition.
In contrast, none of the related patents listed above recites this specific combination of elements. Furthermore, none of these related patents refers to flexographic printing.